Comparing different statistical models for assessing Fe-contaminated soils based on VNIR/SWIR spectral data     

Mahboobeh Tayebi  Mehdi Naderi  Jahangard Mohammadi  Mohammad H. Tayebi 《Environmental Earth Sciences》2017,76(21):734

Two statistical models including partial least squares regression (PLSR) and principal component regression were comparatively utilized to determine the predictive accuracy of visible–near-infrared and short-wave infrared reflectance spectroscopy in quantifying the Fe concentration in contaminated soils. Two scenarios were applied to select the best model: Scenario I included all wavelengths (400–2450 nm) and Scenario II encompassed characteristic bands of Fe. Pre-processing techniques used to select the best model included: first and second derivatives (FD and SD), multiplicative scatter correction (MSC) and standard normal variate. The abilities of the predictive models were evaluated by splitting soil samples into two random groups (80 and 20%). The first group (80%) was used to evaluate calibration and validation sets by employing the cross‐validation method, and the second group (20%) was applied to test the models. The coefficient of determination (R ²), root mean square error and residual prediction deviation were calculated to evaluate the models. Applying Scenario I indicated that the PLSR model with SD pre-processing was a more accurate technique for predicting the Fe concentration, whereas in the Scenario II, the PLSR model with MSC pre-processing had a better performance. Comparing Scenarios I and II indicated that the more reliable models for predicting the soil Fe content could be constructed by the PLSR model with the SD pre-processing techniques and all wavelengths. The modeling results produced by the PLSR model with the SD pre-processing could be used to detect, map and monitor Fe-contaminated soils by proximal and remote sensing in the mining areas.  相似文献   

Performance-based assessment of an innovative braced tube system for tall buildings     

Hossein Mohammadi  Vahab Toufigh  Ali Akbar Golafshani  Ali Arzeytoon 《Bulletin of Earthquake Engineering》2018,16(2):731-752

In this paper, an innovative seismic lateral force resisting system for tall buildings is introduced. In this system, a novel supplemental part, ribbed bracing system (RBSyst), is attached to Braced Tube System, creating a modified BTS. RBSyst is a supplemental part which is attached to the conventional bracing members to eliminate buckling problem. The behavior of RBSyst under tensile force is similar to that of the conventional braces. However, in compression, it prevents the braces from buckling by length reduction. In order to evaluate the efficiency of this new BTS system by performance-based assessment, two typical 40-story tall buildings with different story modules equipped with this proposed bracing system are modeled numerically. Then, the seismic behavior of these 3-dimensional models are evaluated by nonlinear time history analysis under maximum considered earthquakes and service-level earthquakes. The results of the analysis demonstrate that the performance of the tall buildings equipped with this new BTS system is within the acceptable limits under both service-level and maximum considered earthquake ground motions. Additionally, it is shown that RBSyst part can effectively enhance the seismic behavior of BTS systems.  相似文献   

Pan coefficient (K p) estimation under uncertainty on fetch     

M. Mohammadi  B. Ghahraman  K. Davary  A. M. Liaghat  M. Bannayan 《Meteorology and Atmospheric Physics》2012,117(1-2):73-83

The FAO Penman–Monteith (F-PM) method is a frequently applied approach for calculating the daily reference evapotranspiration (ET₀). This method requires long records of meteorological data, which makes it quite hard to employ in locations with no or limited available data. Evaporation pans are widely used to estimate the reference ET₀, but this method requires reliable estimates of the pan coefficient (K _p). The objectives of this study were to determine the proper values of monthly and annual K _p, as well as the best method among those available for the estimation of K _p values in the study area. Measured weather data from 1992 to 2006 were obtained from 18 stations in the North and Northwest of Iran. Daily ET₀ calculated using methods by Bernardo et al. and Pereira et al. were compared with those calculated by the F-PM method. The employed methods at all stations, except those located in the north of the study area with high relative humidity, overestimated the ET₀ compared to the F-PM method. The constant parameters of these methods were optimized by a trial and error scheme to minimize the root mean square error. The results indicated that modified K _p coefficients from Bernardo et al.’s method ranged between 0.41 and 0.87 and the optimal coefficient of Pereira et al.’s method ranged between 0.49 and 0.95. Modified monthly K _p from Bernardo et al.’s method ranged between 0.3 and 1.07 and those from Pereira et al.’s method ranged between 0.4 and 1.18. Modified K _p of the methods by Bernardo et al. and Pereira et al. showed the higher estimation accuracy of daily ET₀ values. In general, the performance of the modified K _p of Bernardo et al.’s method was higher than Pereira et al.’s method for all stations. Thus, in the study region and under the same climatic conditions [in areas with only pan evaporation (E _p) records], the use of climatic monthly modified K _p to calculate ET₀ based on class A E _p is recommended.  相似文献   

Investigation of meteorological extreme events over coastal regions of Iran   总被引：1，自引：0，他引：1  

Safar Marofi  Mohammad Mehdi Sohrabi  Kurosh Mohammadi  Ali Akbar Sabziparvar  Hamid Zare Abyaneh 《Theoretical and Applied Climatology》2011,103(3-4):401-412

In this study, in order to detect probable trends and effects of climatic extreme events of precipitation and temperature as well as maximum relative humidity, dew point temperature, sunshine hours, and wind speed, 12 stations on the northern and southern coastlines of Iran were investigated from 1977 to 2007. For this purpose, 27 indices of precipitation and temperature, which are specified by the Expert Team of the World Meteorological Organization and Climate Variability and Predictability, were calculated by using RClimDex software. The Mann?CKendall method was also used to detect possible trends in the data time series. The results indicate that temperature indices are absolutely consistent with warming. Warm nights, hot days, and hot day and night frequencies increased, while cold spell and cool day and night frequencies declined. The minimum temperature experienced a considerable rise both in its maximum and minimum values. The minimum temperature had a higher increase than the maximum temperature. Therefore, diurnal temperature ranges have experienced dramatic declines. In the northern coastal sites, hot day frequency and hottest day temperature showed higher magnitudes than those of the southern sites as a result of the significant increase in the maximum sunshine hours in northern stations. This enhancement led to a considerable increase in the maximum wind speed. Consequently, relative humidity declined in the northern sites. Precipitation indices indicate few significant trends over the studied period. Temporal precipitation distribution was different from station to station. Three precipitation patterns were detected at individual stations, although an overall regional rainfall pattern was not detectable. On the whole, the results of this study emphasize that the water resources in the studied area are going to become problematic.  相似文献   

Enhancement of Carbon Dioxide Capture by Amine‐Functionalized Multi‐Walled Carbon Nanotube     

Soodabeh Khalili  Ali Asghar Ghoreyshi  Mohsen Jahanshahi  Kasra Pirzadeh 《洁净——土壤、空气、水》2013,41(10):939-948

In this study, crude multi‐walled carbon nanotubes (MWCNT) was functionalized by a two‐step process; first using strong mixed acids (H₂SO₄/HNO₃) and then treatment with 1,3‐phenylenediamine (mPDA). The equilibrium adsorption of CO₂ on pristine MWCNT and amine functionalized MWCNT (MWCNT‐NH₂) were investigated. Experiments were preformed via application of volumetric method in a dual sorption vessel at temperature range of 298–318 K and pressures up to 40 bars. The results obtained indicated that the equilibrium uptake of CO₂ increased after functionalizing of MWCNT. The increase in CO₂ capture by MWCNT‐NH₂ was attributed to the existence of great affinity between CO₂ molecules and amine sites on this adsorbent at low pressures. The experimental data were analyzed by means of Freundlich and Langmuir adsorption isotherm models. The data obtained revealed a fast kinetics for the adsorption of CO₂ in which most of adsorption occurred at initial period of adsorption experiments. This renders MWCNT as a suitable adsorbent for practical applications. Values of isosteric heat of adsorption were evaluated based on Clausius–Clapeyron equation. The results demonstrated that both chemisorption and physisorption played important role in CO₂ adsorption on MWCNT‐NH₂, whereas the physisorption process was dominant for CO₂ adsorption on MWCNT.  相似文献   

Regularization of geophysical ill-posed problems by iteratively re-weighted and refined least squares     

Ali Gholami  Hamzeh Mohammadi Gheymasi 《Computational Geosciences》2016,20(1):19-33

The iteratively re-weighted least squares (IRLS) is a commonly used algorithm which has received significant attention in geophysics and other fields of scientific computing for regularization of discrete ill-posed problems. The IRLS replaces a difficult optimization problem by a sequence of weighted linear systems. The optimum solution of the original problem is usually determined by computing the solution for various regularization parameters λ, each needing several re-weighted iterations (usually 10–15). In this paper, in order to decrease the required computation time (iterations) while maintaining good properties of the algorithm such as edge-preserving, the IRLS is augmented with a refinement strategy and the value of λ is progressively updated in a geometrical form during the iterations. The new algorithm, called iteratively re-weighted and refined least squares (IRRLS), can be interpreted as a Landweber iteration with a non-stationary shaping matrix which is updated based on the solution obtained from previous iteration. Two main properties of IRRLS are (1) the regularization parameter is the stopping iteration and (2) it is equipped with a tuning parameter which makes it flexible for recovering models with different smoothness. We show numerically that both the residual and regularization norms are monotone functions of iteration and hence well behaved for automatic determination of stopping parameter. The Stain’s unbiased risk estimate (SURE), generalized cross validation (GCV), L-curve analysis, and discrepancy principle (DCP) techniques are employed for automatic determination of optimum iteration. Experimental results from seismic deconvolution and seismic tomography are included showing that the proposed methodology outperforms the conventional IRLS with significantly lower computational burden.  相似文献   

A hybrid SVM-FFA method for prediction of monthly mean global solar radiation     

Shahaboddin Shamshirband  Kasra Mohammadi  Chong Wen Tong  Mazdak Zamani  Shervin Motamedi  Sudheer Ch 《Theoretical and Applied Climatology》2016,125(1-2):53-65

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Assessing the accuracy of multiple regressions,ANFIS, and ANN models in predicting dust storm occurrences in Sanandaj,Iran   总被引：1，自引：1，他引：0  

Shahram Kaboodvandpour  Jamil Amanollahi  Samira Qhavami  Bakhtiyar Mohammadi 《Natural Hazards》2015,78(2):879-893

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4‐Phenyl‐3‐thiosemicarbazide Modified Magnetic Nanoparticles: Synthesis,Characterization and Application for Heavy Metal Removal          下载免费PDF全文

Kiomars Zargoosh  Mohammad Reza Mohammadi  Hamed Abedini 《洁净——土壤、空气、水》2014,42(9):1208-1215

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Numerical modeling of flow in riverine basins using an improved dynamic roughness coefficient   总被引：1，自引：0，他引：1  

Siavash Mohammadi  Seyed Mahmood Kashefipour 《Water Resources》2014,41(4):412-420

Various parameters such as bed and bank materials, shape and irregularity of the section, vegetation, river meanders, plan of the river path etc. affect the flow hydraulic resistance. In open channel hydraulics the effects of all these parameters are generally considered as the roughness coefficient. The Manning’s equation is one of the most practical equations to flow resistance analysis, in which the surface roughness is defined by Manning coefficient. Since many parameters are effective on the value of this coefficient, in this research study it was tried to define the roughness coefficient somehow that it be able to dynamically change with different river and hydraulic conditions. The collected data in Karun River (Iran) for two periods were used as the case study. It is shown that the accuracy of model predictions for water surface elevations were improved more than 13% in error estimation in comparison with the corresponding results obtained for a constant roughness coefficient. The roughness coefficient (n) for Karun River was also estimated using the empirical method proposed by Cowan for two different dry and wet periods. These values were then successfully compared with the average corresponding roughness coefficients calculated by the numerical model for those periods.  相似文献